Copolyoxamides



March 28, 1961 c. R. LINDEGREN COPOLYOXAMIDES 4 Sheets-Sheet 1 Filed May 13, 1954 Om mm CON OOm

POLYMER STICK TEMPERATURE C INVENTOR CARL R. LINDEGREN ATTORNEY March 28, 1961 c. R. LINDEGREN 2,977,339

COPOLYOXAMIDES Filed May 15, 1954 4 Sheets-Sheet 2 Fig. Z

STICK TEMPERATURE vs. MOLAR COMPOSITION iN TETRAMETHYLENE-PENTAMETHYLENE-HEXA'METHYLENE TERPOLYOXAMIDES PE NTAM ETHYLENE (52) Boundary between compositions which con be injectionmoulded und Those which cannot.

TETRAMETHYLENE (42) HEXAMETHYLENE (62) INVENTOR CAQL R. LINDEGREN Q. We

ATTORNEY March 28, 1961 c. R. LINDEGREN 2,977,339

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POLYMER STICK TEMPERATURE C INVENTOR CARL l?, LINDEGREN ATTORNEY natasha ,United States Patent() coPoLYoXAMmEs Carl R. Lindegren, New Castle, Del., assigner to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed May 13, 1954, Ser. No. 429,469 1 Claim. (Cl. 260-78) This invention relates to linear copolyoxamides in. whichthe groups separating recurring oxamido groups comprise at least two members of the class consisting of tetramethylene, pentamethylene and hexamethylene groups. V

Heretofore numerous linear polyoxamides have been disclosed. In some instances the physical properties of particular polyoxamides have been studied in considerable detail. In general, however, the lower alkylene polyoxamides have had melting points which exceed, or closely approach the decomposition temperatures of these polymers. For this reason these polyoxamides have not been employed commercially in plastics applications.

For molding operations, and especially for injection molding, it is essential that the material to be molded or shaped be stable at temperatures needed to produce adequate flow. This stability implies constancy of desirable properties, such as toughness', tensile strength, etc., during the shaping process; for injection molding, this constancy of desirable properties should be retained at the temperatures required for adequate ow for a substantial period of time, e.g. about twenty minutes. The polyoxamides exhibit suicient thermal stability for use in injection molding at temperatures up to about 290- 295 C., but to produce adequate ilow in injection molding Vapplications it is necessary to use a cylinder temperature which is at least to 25` 'above the stick temperature(s`tick temperature being defined as the y ,l

temperature at which a specimen of the polymer displays 'a tendency to stick to a smooth surface). Accordingly, a polyoiiamide must have a stick temperature of not more than 278 C., to be a good moldable resin.

Theifollowing vtable shows the stick temperatures 0f polyoxamide homopolymers of straight chaindiamines having from two to ten carbon atoms. For sake of vbrevity a nomcclature system isA herein used wherein the numberiof carbon'atoms Vin the straight chain diamine with terminal NH2 groups is rst designated followed 'by ia number designating the number of linear carbon atoms in' the ydibasic acid component -is decamethylene 4polyoxamide);

(Afor example, 102

AEect of diamine chain length on stick temperature of polyoxamide homopolymers pending application of Stamatof`f,

14, i952, the eiiect'f'vintoducing methyllsub- Y the carbonfatm's of @diamine compo-1, properties of ,66 nylon'is given'injthe follow ICC nieuwe Mar, 2s, 1961 temperature could be lowered by methyl substitution. For example, the stick temperature of 3-methyl72 was found to be 195-205, a suitable temperature for either molding or spinning. The latter polyoxamide was especially attractive in that it also had a resistance to degradation by light which was superior'to that of 66 (hexamethylene polyadipamide). Y

Generally speaking, however, the long chain terminal diamines, and the methylfsubstituted diamines employed by Stamatoi, are sut`n`cient1y expensive to compensate'at least in part for the economic advantage in using a very cheapl dibasic acid, namely, oxalic acid. 0n the other hand, the manufacture of adipic acid by oxidation of cyclohexane (followed by oxidation of cyclohexanol, cyclohexanone and other primary products) produces large amounts of succinic and glutaric acidsy as by-products, and if necessary Vor desirable these materials could be converted to straight chain C4 and C5 diamines by known methods. Since oXalic acid is the cheapest, or one of the cheapest, of the dibasic ac'ids, the raw material situation is thus favorable to the manufacture of polyoxthat specific 'combinations of straight chain diaminoalkanes generally yield copolyoxamides which have low enough stick temperatures, and suiiiciently good thermal stability under conditions of ow, to permit their use in yplastics applications, kespecially in injection-molding. The particular combinations of these diaminespand the relative proportions thereof which produce this useful result, are indicatedy in TablevII.

TABLE 1r v Y o Copolyoxmides of straight chain rdrimr'zes 1 Y Polymer r.'Wateri vStick ,Binh

' tion,

nsolution being the viscosity oi a solution of 0.5.gram of thapoly ml. m-cresol at; 25 C SalI-'e temperature.

Y Aruongthe best compositions listed inlfable areth 42152/62 and z52/62 copolymer compositions. "A 'com parison lof vthe physical properties lof ,the V"preferred 0142/52/62 andj5'2/62 compositions withthe correspondv in p Y nsolvent being'the viscosityof m`cresola`t`the n' TABLE III Properties of 42/52/62 and 52/62 copolyoxamzdes Property 66 Con- Y 42/52/62 52/62 trol (20/60/20) (60/50) Hardness-M Scale 40 92 87 Density 1.14 1. 22 1. 21 Heat dist. temp., 66 p.s.i., C 204 204 200 Heat dist. temp., 26410.55., C- 78 93 94 Tensile strength, 103 p.s.i. 10. 9 12.6 11. 7 Elongation, percent 50+ 30 4-26 Impact strength, 25 C., Izod 1. 0 1. 03 1.07 Mandrel bend. percent tough 100 100 100 Stilncss, 25 C., 10s p.s.i 2. 2 3. 86 4. 33 Deformation (2,000 p.s.i.) 50 C.,

percent 1.4 1. 26 0.62 Water absorption, percent equilibrium 8.3 3. 06 3. 04 Water absorption, percent ASTM.-... 1. 0.35 0.21 Flammability in./min. or in.2/min l SE SE SE l SE-Seli-extlnguishing.

The copolyoxamides mentioned in the foregoing tables were prepared by reaction between an oxalate ester (din-butyl) and a mixture of the diamines. in a generally applicable procedure, which was found to be quite satisfactory, the reactants were mixed in the presence of an inert solvent (alcohols such as methyl, ethyl, 'ri-butyl, etc., hydrocarbons such as benzene, toluene, etc., or other inert anhydrous solvent, can be used) at room temperature without application of external heat, to form a prepolymer, followed by removal of solvent and further heating of the prepolymer at a temperature 2O to 30 above the stick temperature for a period of from ten minutes to two hours. More specifically the process of preparing the copolyoxamides is set forth in 'the following examples.

EXAMPLE 1.-42/52/62 TERPOLYMER (20:50:30)

To a cooled solution of 6.010 g. (.0588 mol) of pentamethylenediamine, 2.169 g. (.025 mol) tetramethylenediamine and 4.189 (.0361 mol) hexamethylenediamine in ml. of dry benzene, was added with rapid stirring 24.161 g. (0.1195 mol) of dibutyl oxalate. The traces of oxalate ester were washed into the mixture with 5 ml. additional benzene. A very rapid exothermic reaction ensued, during which stirring was continued until the prepolymer set up as a white solid. The prepolymer was allowed to stand for one hour under nitrogen and then polymerized for fifty-tive minutes at 274 C. The inherent viscosity of the polymer in m-cresol was 0.96. It had polymer stick temperature of 234 C. and was injection molded at 265 C.

EXAMPLE 2.-52/62 COPOLY'MER (50: 50)

A prepolymer was prepared by the addition with stirring of 23.046 g. (0.1140 mol) dibutyl oxalate toa cooled solution of 5.729 g. (.0561 mol) pentamethylenediamine and 6.7.26 g. (.0579 mol) hexamethylene diamine in ml. of toluene. After standing under nitrogen for one hour the prepolymer was polymerized for fifty-five minutes at 288 C. The polymer had an inherent viscosity of 0.71 and a polymer stick temperature of 243 C.

EXAMPLE 3.--52/62 COPOLYMER (50: 50)

A second copolymer was prepared in a manner similar to that indicated 'in Example 2 using the same propor- 1 the of phosphbrbusadd catalyzed the'poli/medianon.` The' For example, 42/52/62, polymerized in the absence of catalyst had an inherent viscosity of 0.96. A 52/62 copolymer which was prepared from slightly impure diamine had an inherent viscosity of 0.71. Use of phosphorous acid catalyst in a second batch increased the viscosity to 0.84. When the diamine was highly purified a 52/62 copolymer with an inherent viscosity of 1.05 was obtained in the presence of the catalyst.

Among the significant properties which are outstanding in 52/62 and 42/52/62 polymers, fatigue endurance limit (defined as the stress limit below which samples will not fail when subjected to repeated reversed axial stress, i.e. more than 106 times) was particularly favorable (5000 p.s.i.). Compared with 66 nylon, these copolyoxamides exhibited lower water absorption, a high degree of hardness, higher stiffness, and lower creep.

As hereinabove indicated, the stick temperature of the copolyoxarnides depends not only on the nature of the respective diamines, but also on the relative proportions thereof. The relationship between the percentage composition of the diamine in 52/ 62 and 42/52/62 polymers is shown in Figures 1 and 2. Figure 1 shows that the critical range for 52/62 is 15 to 75% (mol basis) of hexamethylene diamine, in the diamine component. Figure 2 shows that the critical range `for 42/52/62 terpolymer isbounded by a curve in `a three component (42-62-52) diagram beginning at about 90% pentamethylene, 10% hexamethylene, 0% tetramethylene, approaching the 42-52 line tangentially at 75% pentamethylene, 0% hexamethylene and 25% tetramethylene, leaving this point and line tangentially, and approaching tangentially the 42-62 line at 65% hexamethylene, 35% tetramethylene and 0% pentamethylene, leaving this line 4tangentially and crossing to a point on the 52-62line at about 75 hexamethylene, 25 pentamethylene and 0% tetramethylene, said boundary constituting an isotherm defining the compositions having a stick temperature of 278 C. Figure 3 shows that in the case of 42/ 62 polymers only a rather narrow range of compositions gives the `desired results, this range being about 57% to 70% hexamethylene diamine in the diamine component. A still narrower range of molar composition (75 to 80% pentamethylene diamine) has a stick temperature at the minimum range needed for plastics application, as shown in Figure 4, when the polymer is 42/52.

Although the percentages hereinabove set `forth define compositions `in which the sole diamine components are tetramethylene, pentamethylene, and hexamethylene n combination, or any two of these components, it will be understood that similar percentage limits apply when very small amounts of ethylene diamine, trimethylene diamine, or in fact any other alkylene diamine o'r mixture 'thereof is used, in Ysuiciently small quantity, in addition rto thezsaid components. This ladditional diamine should not be used in large enough quantity, however, to raise the stick temperature of the multicomponent polymer to above about 278-o C. lIn this connection, it Ais noteworthy that the introduction of 2O mol percent of ethylene diamine (other components being 40% tetramethylene diamine +40%, hexamethylene diamine-cf. Figure 4) resulted in a stick temperature of 266 (cf. Figure 3 for comparison). Thusl it would appearthat when substantial amounts of ethylene diamine are present along with appropriate quantities of the other diamine products of suitable stick temperature are obtainable. Copolyoxarnides prepared from trimethylene diamine were 'found to 'be meltunstable when trimethylene diamine was present in substantial amount in the diamine reactant.

The copolyoxamides of this4 invention are valuable and useful in a variety of injection molding and extrusion applications, including the extrusion of bristles, filaments, etc. ,They canY be produced` as molding powder, and can be 'used as Vsuchlwitljiout,plasticization.` The weathering properties of these polymers are at least `about as good tas the 'corresponding properties of other high quality 5 i nylons, such as 66, and these properties can be further 2,336,824 Wiley Dec. 14, 1943 Y. n Y improved by the use of specific stabilizers. 2,558,031 Allen et al. June 26, 1951,VV

I claim:

A copolyoxamide in which the ygroups separating re- FOREIGN PATENTS curling oxamido groups as integral parts of the main 5 114,623 Sweden yJuly 31, 1945 polymer chain are tetramethylene, pentamethylene and Y hexamethylene groups, in the mol proportions of 20%, (DEER REFERENCES 60% and 20% respectively. Catlin et al.: J. Polymer Science, vol. 2, 1947, pages References Cited in the le of this patent Evans et a1.: J. Amer. Chem. Scie., vol. 72, page 2018. UNITED STATES PATENTS Y 2,252,554 Carothers Aug. 12, 1941 

